What is the main kind of shell insects that harm white orchids? How to prevent and cure?

The shell insects that harm white orchids are mainly chaff scale, Japanese tortoise wax scale, ivy shield scale and so on. their adults and nymphs gather on the back of leaves and branches to suck juice, wilting leaves and sometimes complicated with coal fouling, affecting the normal growth of plants and reducing ornamental value.

(1) bran scale: also known as bran shield scale, gray spot scale, named because of its gray-white shell, showing the shape of bran flakes. The female adult is nearly pear-shaped or oval, lavender and yellowish, with a body length of about 0.8 mm; the female shell is oblong, about 1.5 × 2 mm long, the wax layer is white, grayish white or light brown, the middle part is slightly raised, and the outer margin is inclined. The male adult is lavender, with 1 pair of wings and 3 pairs of feet, and there is no needle-like mating organ in the abdomen; the male shell is slender, gray-white and nearly parallel on both sides. When the nymph is newly hatched, the body is flat, oval, light purplish red, and there is no wax in vitro. The bran film is widely distributed in the north, generally occurring 2-3 generations a year, overwintering on the branches and leaves with fertilized female adults or eggs under the shell, and the first generation nymphs occur one after another in late April of the second year. Bran scale has a wide range of hosts, which is harmful to jasmine, Michelia, camellia and so on.

(2) Japanese tortoise wax scale: also called Japanese wax scale. It is widely distributed in East China and North China, and does great harm to Magnolia, Camellia, Michelia, Mizihua and so on. Japanese tortoise wax mosquito female oval, light brown; shell white or gray-white, about 4 mm long, tortoise shell-shaped depression, central uplift, surrounded by 8 rough protuberances. The male adult is oval, brown, about 1 mm long and has a pair of membranous translucent white wings. The development of Japanese tortoise wax scale can be divided into four stages: egg, nymph, pupa and adult. the nymph is flat, oval, yellowish and 0.5 mm long.

The Japanese tortoise wax scale usually has one generation every year, overwintering with fertilized female adults on the branches and leaves, and the peak hatching period is from the middle of June to the middle of July in the second year.